how to do a proper compression test rb26

[gtrjon]

so i have been reading around on the proper way to do a compression test and read many different ways. so i am just trying to get a answer on the proper way to do it. i have done a compression test on a honda before and i left in 3 spark plugs and only took out the cylinder i was testing. is this in correct? also i read i am supposed to take out the fuel pump fuse? if someone could make a detailed response including all the steps on how to do a correct compression test. detailed as possible thanks guys

[NismoS-tune]

Pull fuel pump fuse, turn engine over a few times till it dies on its own OR disconnect all injector connectors which is more work but better. Remove all spark plugs. Start compression test, 5 cycles each. Write down value and move on to the next cylinder. If you don't have a good battery, have a charger or booster on stand by. Should takes less than 1 hour to do if you're drinking beer at the same time. Have fun!

why are you doing a compression test? You have some problems and are looking for missing HP?

[evilgtr]

Some guys do it with the throttle wide open to not sure if this is correct or not ? Also I unplug my CAS not sure why I just read it on SAU forum. Nothing wrong with doing comp test I do one every time I change plugs or change my oil (1000km or 2 monthes) it's piece of mind and you may catch issues before they get out of hand

[GTRADDICT]

Some guys do it with the throttle wide open to not sure if this is correct or not ? Also I unplug my CAS not sure why I just read it on SAU forum. Nothing wrong with doing comp test I do one every time I change plugs or change my oil (1000km or 2 monthes) it's piece of mine and you may catch issues before they get out of hand

This is how you save money! smart man!

[markc32]

no need to a comp test u can tell if ur car has bad cylinders...just feel it the #s will just piss u off JK....its a good idea to do twice a yer

[evilgtr]

Actually you can't tell when you have bad cylinders all the time, forced air compensate for alot of internal problems you may have that are contributing to lack of power. To prove this is true I will use my car as an example and Cam from light speed will confirm this as he is the one who fixed my head. I had 2 bent valves in #1 cylinder causing compression in that cylinder to run at 70psi. There was absolutely no smoking,no back firing,no excessive heat,no excessive fuel being used,and most importantly - NO LOSS OF POWER. like I mentioned when I change plugs and oil almost monthly regardless of kms I do a compression test since it takes less then 10 mins. This is how I found it. The car would still break all 4 tires loose at 80+ km/hr even with the faulty valves so you are wrong when you say you will feel it.

Twice a year is ridiculous that's like saying check your oil twice a year. For the 15 mins it takes from start to finish why wouldn't you do it a least once a month,also for you track guys and high boost high hp guys you will agree that reading your plugs is a vital way to see how your car is running (rich or lean) I go the extra mile when it comes to my car i want this car to run like it does now in 20 years so being proactive will help find potential problems and fix them before they turn catastrophic.

[NismoS-tune]

yeeaaa the WOT is key there, sorry it wasn't clear lol.

[NismoS-tune]

Companies don't ever compression test cars when you get them serviced, even on new corvette ZR1s, GTRs whatever, even at the end of warranty. It's a peace of mind that can be done. Comp tests don't tell you the condition of rod bolts, valve springs, bearings piston surfaces or other failure points. It's important to do after an engine breal in, before tuning to ensure your rings sealed but really, is it needed so often, like plugs every oil change? ouch. You could do it for assurance that everything is good though. A car will not always run like crap with uneven compression. When I had 2 GTRs, one was stock everything and the other had 300whp. The stock gtr had lower than 140 comp on all and more than 20psi between the highest and lowest cylinders. It was faster than the 300whp GTR still.

If you're doing so many comp tests, plugs every oil change and oil analizing is good to do too. Oh ya, fuel filters may as well be done too, along with intake filters. then you know you're top knotch.

[gtrjon]

yes i realize its not necessary but i am looking for piece of mind. i am about to embark on a build with a stock bottom end and just making sure i am not overlooking anything before i dump a boat load of $$$ into it. thanks

[NismoS-tune]

yes i realize its not necessary but i am looking for piece of mind. i am about to embark on a build with a stock bottom end and just making sure i am not overlooking anything before i dump a boat load of $$$ into it. thanks

Kewl. Like a tuner told me once. Your 20 year old bottom end shows 160psi across the board. So what. That only tells me the seal/compression is good but doesn't confirm the condition of everything else. You could blow a bearing or rod bolt with perfect compression. As long as you don't base the condition of your engine on a comp test, you'll be fine. Some guys have put 450whp on a stock engine and other pop at 300whp. I pulled mine at 300whp with that awesome compression...

Serious power requires serious upgrades to ensure the best reliability.

[evilgtr]

Approach the situation how ever you feel comfortable. I do it for piece of mind, I don't want to find out I could have prevented a problem before it destroyed my engine. Also I do my fuel filter. On a regular basis as well as have my oil analyzed. I have more money then time so I don't f@@k around with my car and want to make sure it's running %100 percent all the time. I don't want to do builds every 2 years

[NismoS-tune]

Approach the situation how ever you feel comfortable. I do it for piece of mind, I don't want to find out I could have prevented a problem before it destroyed my engine. Also I do my fuel filter. On a regular basis as well as have my oil analyzed. I have more money then time so I don't f@@k around with my car and want to make sure it's running %100 percent all the time. I don't want to do builds every 2 years

you're nuts lol. I went with a 10L+ oil capacity to not do oil changes as often cause I hate maintenance attention hungry cars but I do see where you come from. Don't forgot to swap brake fluid every year and rad fluid every spring

[bellis_GTR]

I love this site <3 I too didn't know the proper way to do a compression test. Thank you all!!

[NismoS-tune]

I love this site <3 I too didn't know the proper way to do a compression test. Thank you all!!

then you should try SAU or GTROC. There's way more knowledge about your car.

[Dragon Humper]

You can do it anyway you want, the only thing you must do is the same thing to all cyl. You don`t have to hold the TB open, you don`t even have to pull all of the plugs (allthough this will take a bunch of strain off the starter). Just as long as you don`t change anything in the procedure halfway through your fine. I`m also a fan of the 3 puff and take a reading, I feel it`s more representative of what you really have (you only get about 5 to 10 more psi with 5 puffs anyway and you don`t have to crank as much).


Every month I pull the plugs for inspection and do a quicky comp. test, this year I did it 5 times. It`s just what you do when you have a car that makes more power that it has a right too, currently about 700hp. For guys with a fairly mild car, twice a year is a good idea.




Jon.